Amazon.com: OWC 8GB (2 x 4GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S08P) : Everything Else
Crucial 16GB DDR4 SDRAM Memory Module - for Notebook - 16 GB - DDR4-2666/PC4-21300 DDR4 SDRAM - CL19-1.20 V - Non-ECC - Unbuffered - 260-pin - SoDIMM (CT16G4SFS8266) at Amazon.com